The processing of materials using extrusion techniques and spray nozzles has been used for many years. In particular, in the food, cosmetic and pharmaceutical industry, ingestible ingredients have been subjected to a number of different processing techniques whereby the ingredients are transformed from their original structure into a new form. Such transformation is usually through the application of pressure and heat, as well as various solvents.
There are many forms of spray drying which have been used over the years for a variety of applications. In general, spray drying involves the atomization of a feedstock in aqueous solution into a spray, followed by contact with a drying medium, e.g. air, which results in moisture evaporation and dried particles. The atomization of a feed into a spray results in the breakup of the liquid into droplets which are then dried as they are suspended in a medium of warm or hot air. The nozzles from which the spray emanates can be selected from a variety of different shapes and configurations and can produce a number of different effects. For example, the forces emanating from the spray nozzle can be centrifugal, pressure, kinetic or sonic. Nozzles, which are generally conical in shape, can have grooved cores, swirled chambers or other geometric designs which impart a specific effect or character on the liquid as it is forced through the orifice.
These different designs have been studied extensively, with the result being that little is actually understood with respect to the subtleties of droplet formation in spray drying equipment. While a number of theories have been advanced to explain the formation of droplets and their variation, the complexity of droplet formation has defied precise empirical correlation. In fact, depending on the pressure, type of liquid used and nozzle type, only general conclusions have been reported in the literature. Such conclusions include the observation that the discharge velocity of the droplet from the nozzle greatly impacts the fineness and size distribution of the resultant droplets. Additionally, it is recommended by some experts that the best atomization is obtained by keeping the discharge velocity of the liquid from the nozzle above a certain minimum.
In addition to the drying steps involved in standard spray drying processing, spray chilling or spray congealing of materials has also been widely used. For example, it is known to take fats which are solid at room temperature, melt them to a liquid and spray them from a nozzle into a cooled chamber where the droplets solidify. In these processes, the fat is subjected to temperatures for a relatively significant amount of time such that the fat is above its melting point and in the molten state. These conditions are necessary to properly process the fat into congealed droplets and to prevent clogging of the processing equipment.
There are several drawbacks to conventional spray drying or spray congealing methods. First, these processes result in subjecting the material to be processed to a significant heat history, which in the case of heat sensitive materials is unacceptable. For example, in the case of highly volatile flavor oils or heat sensitive sweeteners such as aspartame, exposure to heat causes loss of their ability to fully perform. The same applies to pharmaceuticals which lose their activity if exposed to excessive heat. Additionally, the heating chambers which are required to evaporate the water or other solvent in conventional spray drying methods are costly and inefficient.
Second, spray drying is commonly conducted in aqueous media whereby the water is removed during the drying process. The use of water or other solvents requires extra measures with respect to processing and disposal equipment, all of which also add to the cost of the process and system, and prevents the incorporation of water sensitive materials. Additionally, spray drying is a relatively low output process, requiring high amounts of energy to evaporate the water. This, of course is energy inefficient.
In spray drying and spray congealing processes, the feedstock material is heated to its molten state in a mixing vat and pumped into a feedline which is connected to a nozzle. The feedline and nozzle must be kept at elevated temperature to keep the feed material flowing. In the case of fats which are solid at room temperature, sufficient heat must be applied to keep the fat in the liquid state, both in the mixing vat as well as during its transport to the nozzle head. In the case of spray drying, heat is further applied in the form of hot air which is used to dry the droplets as they emanate from the nozzle.
The application of heat throughout all phases of the conventional spray drying and spray congealing processes is costly and requires control features which must be monitored. Additionally, the amount of space required to conduct the conventional processes is large and therefore costly. This is due to the need for a large volume used to dry or cool the particles, typical of the fluidized bed type processes.
Furthermore, conventional spray drying or spray congealing processes require the feed material to sit for relatively long periods, i.e. hours, in the liquid state while they are waiting to be pumped into the feedlines and subsequently sprayed. This waiting period creates a heat history which, as previously discussed, is deleterious to heat sensitive materials which may be present in the feed material, e.g. volatile flavor oils, heat sensitive sweeteners and pharmaceuticals. Furthermore, the conventional processes require dispersing agents to keep components in the molten mixture from settling out prior to and during pumping to the nozzle.
Additionally, in prior art spray drying or congealing methods variables such as pressure, temperature, nozzle type and material type must be balanced to produce a consistent particle size. These variables are such that it makes predictability of the character of the final product difficult at best to determine. Additionally, even under the best of conditions, uniformity of content of the particles is not necessarily controllable. Particles formed from spray drying or spray congealing can only have uniformity of content if they are the same size and are made from a homogenous mixture of ingredients, i.e. a blend of materials.
More recently, an apparatus and method for processing feedstock has been described by Dr. Richard Fuisz in copending U.S. Ser. No. 07/965,804 entitled "Process For Making Shearform Matrix". This application relates to a unique process and apparatus for making a matrix using fluid shear force. The process involves controlling the temperature of a feedstock which includes a solid non-solubilized carrier material to the point where the feedstock undergoes internal flow. The flowing material is then ejected as a stream under pressure from an orifice which is then disrupted by a fluid shear force as it emanates from the orifice. The fluid shear force is preferably air. This application describes apparatus which is useful in the present invention and is incorporated herein by reference.
The present invention seeks to improve on the prior art techniques of spray drying or spray congealing and overcome the disadvantages associated with these techniques. A new form of product has been discovered using flash flow processing techniques. This new form has been termed a "solloid", the definition of which is discussed further herein. The solloids of the present invention are solid suspensions, i.e. a solid suspended in a solid, which are formed by using flash flow processing and disruptive fluid shear forces to form discrete, uniform spheroids under extremely low pressures as compared to the prior art processes, and with minimal exposure to heat. The present invention seeks to avoid temperatures above those which are necessary to achieve a flow condition of the matrix material being processed, which in most instances will be below or close to the melting point temperature. The temperature required to create the flow condition, however, must not be such that it reaches the melting point of the non-fat solid substrate in the fat matrix. Additionally, the time period during which the feedstock material is subjected to these temperatures is very short, i.e. on the order of tenths of a second in the flash heat method and on the order of seconds in the flash shear method.